The present invention relates to drainage grates used in connection with trench drains and the like for the drainage of surface water. Trench drains and similar drainage structures are used in a variety of environments, such as walkways, bike and foot paths, outdoor malls, parking lots, airport tarmacs and other traffic environments which require the drainage of surface water. Trench drains and drainage structures generally are known in the art as described in, for example, U.S. Pat. Nos. 4,630,966; 4,699,544; 5,462,382 and 4,553,874, incorporated herein by reference. In order to provide access of surface water to the drainage structure, while at the same time enabling practical movement of traffic across the structure, apertured drainage grates are typically employed to provide a substantially continuous surface over which pedestrian or vehicle traffic can freely move.
Drainage grates are typically made of varying gauges of sheet metal and are, therefore, subject to damage. Dents, buckles and perforations in the drainage grate are not only aesthetically undesirable, but are also safety concerns which can lead to injury to pedestrians and damage to surface vehicles. Accordingly, drainage grates must meet particular load ratings depending upon the environment in which they are to be used. Although there is no universal system for load rating of trench drains, the internationally recognized DIN 19580 standard, incorporated herein by reference, provides a good basis on which to distinguish between classes. Basically, for trench drains under 8 inches wide, a class A rating will withstand 15 psi within the standard 3 inch by 10 inch load footprint, and is typically used in residential and light pedestrian areas. A class B rating will withstand 140 psi in the load footprint, and is typically used for sidewalks and small private parking lots. A class C rating will withstand 280 psi in the load footprint and is appropriate for commercial parking lots and the like. Classes D and above will withstand 450 psi or more in the load footprint and are found in roads or other areas experiencing heavy wheel loads.
The requirement for different load ratings typically means that a manufacturer must provide different grates for different applications. Thus, in practicality, a manufacturer must provide grates of different gauges and materials or which include various reinforcements appended thereto. However, there are practical limits to the gauges of metal which can be used and, even when various reinforcements are included, they do not provide continuous support to the entire drainage grate surface. Thus, even a reinforced grate is still subject to damage in those regions which are not directly reinforced.
In view of the foregoing shortcomings, the present invention advantageously provides a reinforced drainage grate which provides continuous support to all or most of the drainage grate surface, and which can provide a wide range of load ratings without having to manufacture and inventory different grates for each desired load rating.